Despite an abundance of research regarding parameters governing tissue injury during ischemia the critical factors determining cell death and organ failure are not well defined. Ischemic disease of the heart, brain and kidney remain major causes of morbidity and mortality. The long range goal of the proposed research is to learn more about the cellular biology of anoxic and ischemic injury in order to establish a well guided approach to the prevention and therapy of ischemic tissue damage in man. In this proposal we have delineated studies designed to evaluate the role of high energy phosphate compounds in cell death associated with oxygen deprivation. The specific aims of the research proposed are three: 1) to establish whether post-anoxic recovery of myocardial and renal cells is determined by the absolute levels of cellular ATP at the end of the anoxic period; 2) to determine whether inadequate availability of nucleotide precursors limits post-anoxic recovery of cellular ATP levels; and 3) to establish if post-anoxic recovery of cellular ATP levels determines recovery of cellular functional viability. Experiments will be performed in isolated cardiac myocyte and kidney tubule preparations. This approach will permit the study of the direct cellular response to amoxia, acidosis, substrate depletion and exposure to excess metabolic waste products. Viability can be defined in vitro and changes in viability due to variation in the noxious stimulus or in the presence of potential protective agents can be defined devoid of the uncertainties of neuronal, homonal and vascular influences present in vivo. The pattern of change in cellular nucleotides, nucleosides and purine bases will be established under the different adverse conditions as well as after return to a nutrient environment, and these will be correlated with multiple determinants of cell viability. Nucleotides, nucleosides and purine bases will be determined by high pressure liquid chromatography. Experimental maneuvers or pharmacologic agents which result in enhanced post-anoxic recovery of cellular functional viability will be studied in detail. Understanding of the mechanism of a protective effect will provide us with a rationale to extend these in vitro studies to in vivo organ studies and provide a rationale for an appropriate therapeutic approach aimed at preservation of ischemic tissue.